Typically, a canister collects fuel vapor evaporated from a fuel tank. The canister also allows the fuel vapor to be burned in a combustion chamber, thereby preventing leakage of the fuel vapor into the atmosphere. The canister typically includes a vent-hole for adjusting the pressure of the fuel tank and purging the collected fuel vapor into the air intake system of the engine. The vent-hole communicates with the atmosphere for allowing air to be taken into the canister from the atmosphere. Accordingly, leakage of fuel vapor from the canister through the vent-hole should effectively be minimized.